The invention relates to a belt-buckle tightener for a seat belt system in a vehicle.
A belt-buckle tightener is disclosed, for example, in EP-A1-0662408 (incorporated by reference herein). The function of a belt-buckle tightener of this type is based on the fact that a piston which is connected to a belt buckle via a draw-in cable is displaced by means of a pyrotechnic charge in order thereby to tighten the belt in the event of an accident.
A particular disadvantage of a belt-buckle tightener of this type is the structural space which is required for the pyrotechnically driven pistons.
DE-A1-4319955 (incorporated by reference herein) discloses a belt-buckle tightener in which a rotary actuator is used instead of a pyrotechnically driven piston. The rotary actuator is actuated by a pyrotechnic driving unit. In addition, an arresting device in the form of a rack is provided and is intended to prevent the belt buckle from shifting counter to the tightening direction. At any rate, the rotary actuator of this belt-buckle tightener requires less structural space than a pyrotechnically driven piston. Nevertheless, even here the rotary actuator, the pyrotechnic driving unit and the arresting device require a large amount of structural space.